Rhododendrons continue to brighten and perfume the Winterthur garden. We don’t know the stories behind all the cultivars but one is particularly telling in respect for Mr. du Pont’s prestige in the horticulture field. Joseph Gable, one of the pioneering azalea and rhododendron hybridizers of the early twentieth century wrote the following to H.F. du Pont in June 1955.

“The plant of Rhododendron “Gable’s Pink #2” – (until it is introduced and I find a better name for it) was settled for by Mrs. Dean and Mrs. Ross when they were here and is their gift to you though it is a plant not yet released to the trade and I made something of a special dispensation in allowing them to have it for you.”

Rhododendron ‘Robert Allison’

Mr. Gable did find a better name for it and called it Rhododendron ‘Robert Allison’. It has lovely, fragrant pink flowers in bloom now on a tall plant, easily reaching 10’. Its sister seedling is named ‘Cadis’ and also offers fragrant pink flowers in early June.

Rhododendron ‘Cadis’

You can find additional early June flowering broadleaf rhododendrons by other breeders in Azalea Woods and near the museum store. Colors will vary from lavenders, pinks, red and white. Another wonderful way to extend the season of color in the garden.

R. hybrid soft mauve

R. hybrid soft mauve

Rhododendron hybrid soft mauve is just opening this week and also offers good evergreen foliage which covers the entire plant. You will find it at the entrance to the Visitor Center and above the Museum Store on Clenny Run.

R. ‘Lady Eleanor Cathcart’

R. ‘Lady Eleanor Cathcart’

We received ‘Lady Eleanor Cathcart in 1955. It tends to be more open but the space below can be used to grow shade loving perennials such as ferns.

R. ‘Mrs. Charles S. Sargent’

R. ‘Mrs. Charles S. Sargent’

‘Mrs. Charles S. Sargent’ was probably in the garden at least by the mid-1960s and is one of our shorter broadleaf rhododendrons. It can be found in Azalea Woods.

Rhododendron ‘Chionoides’

Rhododendron ‘Chionoides’ arrived in 1965 and is now one of our largest and widest rhododendrons. Discover it in Azalea Woods just past ‘Lady Eleanor Cathcart’. Rhododendron discolor and Rhododendron maximum will soon join the show and extend the color through the month of June.

WINTERTHUR BLOOM REPORT #07May 27, 202079F, sunny

+: Abundant
fbb: Flower-bud breaking
b: Some bloom
fb: Full Bloom
pf: Petals falling/drying
pb: Past bloom (few remain)
ber: Berries, fruits
.Check these out:
 The peonies in the Peony Garden and the candelabra primroses (Primula japonica) in the Winterhazel Walk area and the Quarry Garden are spectacular shows of color.
 Take a deep breath to experience the fragrance of the fringe trees (Chionanthus virginicus) blooming at the Icewell Terrace side of the Pinetum and on Sycamore Hill.
 Enjoy the walk from the Fish Ponds to the Bridge – it’s a magnificent lush ‘velvet’ carpet of green moss.

 Found throughout the gardens but mentioned only here:
o Look up to see the green & orange tulip tree (Liriodendron tulipifera) flowers – or down on the paths to see flowers or pieces of flowers throughout the gardens.
o The tiny white, sometimes pale pink, daisies of fleabane (Erigeron annuus) are scattered throughout the meadows & gardens.

“The longer I grow azaleas, the more I realize how beautiful they are when grouped in harmonious colors and pleasing contrast. They naturalize in every imaginable terrain and contour (no other species are in bloom in Delaware for almost four months) and due to their various height and habit of growth are never monotonous, and are perfect with countless varieties of bulbs and wild bloom”. Mr. du Pont wrote these words in 1962 for the Quarterly Bulletin of the American Rhododendron Society.

Kaempferi hybrid azaleas at the Icewell Terrace

This week he may have been referring to the harmonious colors and contrast provided by his kaempferi hybrid azaleas. Like many of our plants, he received these azaleas from the Arnold Arboretum. They start to flower in mid-May and will continue to early June. We have two color strains. One strain ranges from salmon to red and the second is a vibrant pink.

Kaempferi hybrid azaleas near Icewell Terrace

Kaempferi hybrid azalea at entrance to Enchanted Woods

We have very little information about these azaleas. Plant maps from the mid-1960s simply list them as late kaempferi hybrids and then color descriptions such as late large red, red pink, large salmon pink for the first color strain and soft rose, pure pink, soft lavender pink for the pink forms. Du Pont kept these two strains near but separate from each other.

Kaempferi hybrid azalea 2819

Kaempferi hybrid azalea 2821

Kaempferi hybrid azalea 2818

Kaempferi hybrid azalea 2820

Kaempferi hybrid azalea 2815

Kaempferi hybrid azalea 2773

Interesting that he did not number the individual color variations within these strains since they are slightly different in color and timing. We are working to do that now so that we can document and preserve the original design by propagating the needed azaleas. He did select one of these and named it ‘Winterthur’. It is a lovely salmon and the plant tends to have a lower habit than the other hybrids. Standing at the conservatory, you can see it on the lawn looking up toward the 1750 house and also lining the entryway to the Pinetum.

In the botanical world, a sport is a genetic mutation that occurs in a segment of a plant. It causes a difference in the appearance of the effected part. In flowers, it is often stripes or portions of a different color or the entire flower may be a different color. If the sport is stable, a cutting from that branch will have the same trait. When Mr du Pont saw one that he liked he did just that. A few of Winterthur’s azalea routinely throw sports each year. One of our Kurume azaleas, #09 in Azalea Woods is an extreme example of this.

Azalea Kurume #09

Azalea kurume #09 in Azalea Woods, May 6, 2020

An example of where H.F used this to great advantage is with our mucronatum series azaleas. These azaleas will begin to flower while the kurumes are still in flower but will continue the display later into May. Based on the quantity of plants, one of du Pont’s favorites was ‘Magnifica’. He used it throughout the garden.

Azalea ‘Magnifica’

It commonly throws two sports, one an entire lavender flower with a similar strawberry blotch or it goes to white. Mr du Pont had these propagated but not named. The white form creates interesting sports as well.

Lavender sport of azalea ‘Magnifica’

Typical ‘Magnifica’ on the left with white sport coming from the same branch

Partial lavender sport on white azalea

We have a similar cultivar to ‘Magnifica’ but with a less intense pink blotch. The unconfirmed name is ‘Sekidera’. It also throws a lavender sport. Mr. du Pont propagated this one and named it ‘Winterthur’. In the photo below, a separate plant of ‘Winterthur’ provides the mass of lavender flowers in the background behind a plant of ‘Sekidera’ featuring the ‘Winterthur’ sport. Note a partial color sport beside it.

‘Sekidera’ with lavender sport

Each of the mucronatum azaleas featured here can be discovered by the Reflecting Pool. ‘Magnifica’ along with its sports and ‘Winterthur’ can be found throughout the garden in both sunny and shady conditions.

In 1930, H.F. du Pont visited Charles Dexter, an industrialist turned rhododendron breeder. Mr. du Pont wrote that he did not know when he had enjoyed anything more and was fired with a desire to plant azaleas in all directions. Dexter’s broadleaf rhododendrons also intrigued him, he wrote, “I shall like to have any number of your fortunei hybrids the minute they are ready to bloom. Please put me down for a large number of these.” Dexter did just that, sending down flats of young plants from his propagation work along with plants with specific colors chosen by H.F.
Du Pont then numbered these in the order that they came into flower in season. Our numbers range from 1 to 53, with #1 being the first to flower in early May and #53 in late May. Number #1 and #7 are similar in flower color and are used together in the garden.

Rhododendron Dexter #01

Rhododendron Dexter #7

Number 6 will open during this same time. Du Pont described its color as tan. Our #18, later named ‘Hal Bruce’ for a former plant curator at Winterthur, is used alongside of it. Hal Bruce is pinker and will be a taller plant.

Rhododendron Dexter #6 (‘Tan’)

Rhododendron Dexter #18 (‘Hal Bruce’)

While Tan and Hal Bruce are in full flower, the Dexter 35 series will begin to open. There were five plants so similar that du Pont called them 35A, 35B etc. His color description of these was ashes of roses. Seen here in bud with the flowers of azalea Kurume #47.

Azalea Kurume #47, Rhododendron 35 series

We have a range of rhododendrons in the perhaps more traditional colors of pink and lavender.

Rhododendron Dexter #27

Rhododendron Dexter #28

In contrast with these, du Pont used his #11, cherry red. These early red types had the disadvantage of having a very open habit. You might notice that even from the image.

Rhododendron Dexter #11

Many of our rhododendrons are the original plants from the 1930s. We have been propagating them with the goal to have at least three plants of each to insure that we preserve them for future generations. Please mark your calendars for this time next year to discover and enjoy the subtle and not so subtle differences in these special plants.

Rhododendrons in Azalea Woods with dame’s rocket and Spanish bluebells

In 1917, H.F. du Pont purchased some of the first Kurume azaleas available in this country. He had these propagated over the years and arranged them to create beautiful corridors of color in what is now known as Azalea Woods. H.F. was keen on creating a seamless beauty but he also loved to collect. He blended these interests by carefully noting color, form and flowering time. One example of this is at the entrance to Azalea Woods with a combination of three similar colored Kurume azaleas with a backdrop of a darker pink.

Kurume azaleas with Spanish bluebells

One of these is called Kurume #47. It is called an irregular hose-in-hose; there are two sets of petals but the back ones are cut and vary in length.

Azalea kurume #47

Azalea kurume #46 on left and kurume #48 on right

The other two azaleas are singles. Kurume #46 is slightly lighter in color with less flecking on the upper petal as opposed to Kurume #48, slightly darker with red flecking.

Mr. du Pont repeated this concept of using similar plants in white at the center of Azalea Woods.

‘Rose Greeley’ azalea on left and kurume #16 in back

Rose Greeley is a hose-in-hose azalea hybridized by Joseph Gable. Kurume #16 is a single and believed to be one of the original azaleas that du Pont acquired in 1917.

‘Rose Greeley’ azalea

Azalea kurume #16, small single white

‘Snow’ azalea (hose-in-hose type)

A bright pink example is provided by azalea ‘Hinomayo’ and two Kurume azaleas that we have given a numbered identification to until we can discover their true names or du Pont’s number.

‘Hinomayo azalea on left, Kurume 0776 in center, 0775 on right

‘Hinomayo’ azalea

Azalea kurume 0775

Azalea kurume 0776

Winterthur is truly a garden that can be appreciated on many levels. Mr. du Pont used this same idea earlier in the season with snowdrops and daffodils and repeats it later in the season with peonies and lilacs. What a great way to have a collection and a beautiful display.

The Winterthur garden provides not only wonderful spring color but also amazing details. The unfurling fronds of ferns are just one example of that. Even at this young stage, it is easy to identify certain ones. It is also a great time to think about how you might use them in your landscape. There are ferns that can provide either an extensive groundcover or an architectural focal point. Below are images of just a few that are unfolding now.

Ostrich fern,Matteuccia struthiopteris, is the predominant fern on the March Bank. Given a moist, shady area, it will happily spread by sending out rhizomes. Great if you have a large area to cover and it will readily come through Japanese pachysandra as seen below. It also combines well with the early bulbs of snowdrop, winter aconites and glory-of-the-snow that have already flowered on the March Bank. Ostrich fern is one of our tallest ferns, sometimes reaching 3’ in ideal settings.

Ostrich fern on the March Bank, late April.

Ostrich Fern is deciduous and it bears it spores on a separate frond, the two brown stalks shown here. These stalks persist through the winter and can be used in floral/Yuletide arrangements.

Ostrich fern

If you would like a tall fern but don’t have the spreading space for ostrich fern then cinnamon fern,Osmunda cinnamomea, is an excellent choice. It can reach 3 feet and will stay in place. Because it is deciduous and later to leaf out, it is also a good companion with Japanese pachysandra and late winter/early spring flowering bulbs.

Cinnamon Fern at Reflecting Pool

It can be identified at this early stage by the silver hair on the young fronds. Later, its cinnamon-colored spores add interest and are a key identification feature.

Cinnamon fern

Cinnamon fern with spores – late May

Royal fern, Osmunda regalis, is another fern to consider if you are looking for a non-aggressive, tall fern. Its unique structure adds contrast to other ferns and perennials. Like the other ferns listed here, royal fern is native to North America and will do best in moist soil. It is sometimes called the flowering fern because of the appearance of it spores.

Royal fern in late April

Royal fern with spores in June

Lady fern, Athyrium filix-femina is a deciduous slow spreading fern that will reach about 2 feet. The stems can be green or red. Specific cultivars such as ‘Lady in Red’ will guarantee that you purchase one with red stems. Lady fern is a good choice if you would like a groundcover fern but one that won’t take over.

Lady fern in April with foliage of winter aconites

Lady Fern cv. Lady in Red

Christmas fern, Polystichum acrostichoides, is an evergreen fern. For ferns, that means its leaves will stay green through the winter and then start to die back in spring, as the new leaves are unfolding. You can either leave the old foliage and let the new fronds cover them or remove them if you prefer a tidier appearance. Christmas ferns are one of the best choices for heavy shade areas.

Christmas fern – late April

Christmas fern- note last year’s leaves

These are just a few of the fabulous ferns at Winterthur. They are all easy to grow and are readily available from nurseries.

The hori hori, often referred to as a “soil knife”, is a must-have garden tool. First implemented in Japan, the tool can be described as a cross between a knife and a garden trowel. It has a heavy, steel blade that is sharp on one edge and serrated on the other, with an overall shape that is slightly concave. The word hori means “to dig” in Japanese. The tool, in fact, is good for digging and so much more. It can be used for weeding, planting, transplanting, removing plants, dividing perennials, sod cutting, cutting roots, loosening up root bound plants, planting bulbs, cutting twine, and cutting open bags of potting soil. You get the idea! With a large, comfortable handle the hori hori is designed to be used with one hand but can accommodate both hands when extra leverage is needed, such as when prying plants from the ground. With the use of an accompanying sheath, the tool is completely portable and within easy reach. The rust-resistant blade promises years of tough use in any garden setting. I use this tool more than any other hand tool, as a horticulturist at Winterthur as well as in my home garden.

When managing the natural lands, I’ve found it’s almost like a strategy game. Which areas need the most attention right now? Which will need attention in 2 weeks? In 3 months? Right now, in spring, I always have a few things on my plate. After mowing the meadows, I usually turn my attention to the woodlands. With our beautiful native spring ephemerals blooming in the woods, it’s a good time to figure out what doesn’t belong. Without fail, one of my least favorite invasives always rears its head: Garlic Mustard!

Garlic Mustard (Alliaria petiolata) is a broadleaf biennial in the mustard family native to Europe and Asia, but has happily made a home here in woodlands, road edges, and shaded floodplains. It’s easily identifiable from the garlicky smell of the plant, round, slightly toothed leaves, and white, 4-petaled (cruciform) flowers that shoot up from the basal rosette in April-May. While the basal rosette of leaves is present year round, the flower shoot is specific to second year plants, and is present April- June. The plant can reach up to 3 feet tall, and the seed pods are slender capsules typical of the mustard family called siliques.

Garlic Mustard with native Virginia Bluebells

Visible- round, toothed leaves and cruciform, white flowers

So, why do I have so much dislike for this plant? Well it all comes down to ecology. Garlic Mustard has a mechanism called allelopathy. Basically, this means that the plant emits a chemical from its roots that disturbs the natural soil chemistry. This prevents native plants from growing, native seeds from germinating, and encourages more growth of Garlic Mustard. Slowly, it can decrease the natural diversity of native plants in a wooded ecosystem. When a monoculture of Garlic Mustard occurs, it can lead to poor soil nutrient cycling and soil health decline, as well as a decline in the diversity of animals and insects that rely on native plants to survive.

Fortunately, this nasty plant is most effectively controlled by hand pulling! For me, this time of year before the plant goes to seed is the ideal time to pull this plant aggressively. I like to pull the plant from the base as close to the soil as I can get, and gently pull it out of the ground. Especially after a rain, it comes right out- roots and all! A little shake to knock off excess soil, and it’s into the weeding bucket. Be sure to go at a nice steady pace. Too fast, and you may inadvertently break the plant at the root since the main tap root usually juts sharply to one side. This can lead to re-sprouting later in the season.

Main root juts to the right

At this point in the development of the plant, I can usually compost it without issue. If composting isn’t an option, and I have to leave the plants behind, I’ll take my bunch of pulled plants and prop it up against a tree with the roots in the air so that the plants dry out and die without re-rooting.

Roots in the air to prevent re-rooting

If the plant has any seed capsule development at all, I will bag the plant and throw it away. These seed capsules can still mature and spread seed- even after it’s been pulled! Because the seeds can persist in the soil for a long time, this is a process I’ve had to repeat in various woodlands throughout the property for a few years. But every year, I notice the decline in the Garlic Mustard population! It’s the long game with Garlic Mustard, but one worth the effort.

This blog comes out on the eve of what would have been our 6th annual Daffodil Day; a Saturday set aside in mid-April to celebrate the daffodils planted during H.F. du Pont’s lifetime. Though some varieties may be found planted within garden areas such as the Quarry, March Bank and Sycamore Hill, the wider displays are naturalized in the fields alongside the garden, lining the front drive and in the cutting garden, an area off the beaten path where flowers would be picked for fresh displays in the house.

The daffodils at Winterthur are older varieties (this should not be to anyone’s surprise!) some dating back to the late 1800’s and early 1900’s
Unlike what we might do in our own home gardens, H.F. did not just open up a catalog, choose a few dozen cultivars and plant them. He used the same scrupulous eye in the creation of the daffodil beds as he did with the rest of the flowering combinations throughout the garden. He set up trial beds where he would observe the color, timing and persistence of the flowers over several years before placing them out in the garden, making sure to group “like with like” meaning daffodils that shared the same flowering time, beds that contained only a single variety within, and harmonious shades next to one another. The countless flowering displays and vignettes throughout the garden are all the result of an impassioned “head gardener” with a skillful eye.

One of my favorite things to do during daffodil season is to encourage visitors to follow directional white arrows and venture out into the meadow to walk among the daffodils, seeing the varieties up close and viewing the whole display and the garden from a vantage point that is different from the norm. Since that is not available to visitors this year, I will do my best to bring it to you. I have taken photos of the many varieties and ones that I might be a little partial toward (creative license!)

The daffodils greet you virtually now but look forward to seeing you live next spring! Enjoy the tour.

Daffodils along the Front Entrance drive.

White daffodils and clouds against the blue sky.

Daffodils with the Needle’s Eye folly in the background.

Daffodils in Browns Meadow with cherries in the distance.

Another long view into the garden toward the Mirrored Folly.

Daffodils near the sycamore.

Daffodil beds below Brick Overlook on Sycamore Hill.

Carpet of daffodils flanked by fragrant viburnum leading down to the Sundial garden

Now for a few closeups! I am partial to orange cups as well as small cup varieties but threw in some fun doubles, too.

Daffodil with spring beauty carpet below.

The buds on this cultivar are just as attractive.

A very large trumpet in Browns Meadow.

I will end with a video of the planting along the front drive. There are many many sounds of nature accompanying it; songbirds, spring peepers, Canada geese, so turn on the volume for the full experience!

About this Blog

The Winterthur Garden Blog is the official Web log of Winterthur Museum, Garden & Library. The blog offers behind-the-scenes information and personal perspectives on the garden, written by the people who work and volunteer here.

Subscribe to Blog via Email

Enter your email address to subscribe to this blog and receive notifications of new posts by email.